Okay so, in my superhero setting, the way humanity gets superpowers is due to a single mutation. People rarely had superpowers before due to the Dragon gene, but it was always a recessive trait and being Dragonbreed meant you were infertile.

However at some specific point in history, a person named Kurt Snow - also an adventurer named The Claw - is born with a mutation that allows him to easily pass on the Dragon gene. And since he's immortal and prone to romances, he basically single-handedly passes his mutated genes to human population over the course of next couple centuries. I imagine he might have somewhere like 500-1000 children, but by modern 21st century superhumans are relatively common and huge chunk of people have that gene, active or not.

So... this kind of math is something that's too much for me to wrap my head around. Basically I'm asking is in what century does Kurt Snow need to be born for it to be reasonable that this mutated gene would become somewhat common in modern population?

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    $\begingroup$ My quick approximation is that this population would about double every 20 years so to reach population-level order of magnitude it might take like 40 000 years... so this would honestly begin in early human prehistory. But I have no idea. Also population growth wasn't linear through history so idk. $\endgroup$
    – shinobody
    Aug 1, 2023 at 14:21
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    $\begingroup$ Depends what you mean by "somewhat common". 1%? 40%? If there were twenty people in the UK (3.3*10^-9%) who could fly, would that be considered somewhat common? $\endgroup$ Aug 1, 2023 at 14:45
  • $\begingroup$ Also, does it make them more apt to survive and reproduce? Are they anonymous? Do people want to mate with them because of their status, women particularly responding to status cues that a superhero might fit? One (or two) fertilised women per night for a superstar-superhero might result in an awful lot of super-babies... What about parental responsibility for rearing/financing? At what point does the pressure on them to take responsibility slow down their nightly "action" with partners? $\endgroup$ Aug 1, 2023 at 14:53
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    $\begingroup$ As for the question you've asked... as it stands, it should probably be closed as "needs more details." Frankly, 500-1000 children is a drop in the bucket for an immortal operating for centuries. At a single hook-up each night for just 200 years and 100% successful impregnation he'd have 73,000 children and hundreds of thousands of grandchildren, etc. But that's a drop in the bucket when it comes to spreading your royal oats across an entire world. Not enough details., Too many variables (infant mortality rate? Cultural hatred for the gene? War/Disease?). $\endgroup$
    – JBH
    Aug 1, 2023 at 15:20
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    $\begingroup$ Genghis Khan genes are in about .5% of the population 750 years later. Which might be a starting point $\endgroup$
    – Styxsksu
    Aug 2, 2023 at 14:50

3 Answers 3


Perhaps the best model for this would be lactose tolerance. Scientists believe that adult lactose tolerance, which is the rule in Europe (between 80% and 100% of the population), first arose from a single mutation of a man in Turkey. It spread faster than biologists believed that genes could spread. Within a few thousand years, it prevailed.

Note that this is more than the "common" you requested, and also occurs without the gene's super heritability, and without an immortal continually adding more of the original gene. A few centuries would therefore be plausible for the gene to spread. But watch where the guy goes. The supers will be concentrated there. (There are places other than Europe where adult lactose tolerance prevails. It appears to be other mutations.)

  • $\begingroup$ This is exactly what I need, thank you so much. $\endgroup$
    – shinobody
    Aug 2, 2023 at 21:06

Making a few assumptions:

  • the hero has 10 children a year
  • the children each have two children (at 20 and 22 in my simulation), and everyone lives until they're 70
  • all the children's children have the super power

You'd have approximately 10,000 supers in a century, 285K in 200 years, 7.7 million in 300 years, and 20 million in 400 years, and a billion by 600 years out.

Lots of assumptions there, but if your dude is more than a 1000 years old you could plausibly have as many supers running around as you like.

See also:

  • $\begingroup$ "All the children's children" cannot possibly have the super power. The chances of a child to inherit a specific gene from a parent is 50%. The chances of grandchildren to inherit a specific gene from a grandparent is 25%. Even if I were a lineal descendant of Charlemagne, who lived about 40 generations ago, my chances of having inherited a given specific gene from him is very low. For example, the lactase persistence mutation arose somewhere in western Europe some 15,000 years ago; obviously beneficial, yet about 1/3 of Europeans still don't have it, and it is very rare in eastern Asia. $\endgroup$
    – AlexP
    Aug 1, 2023 at 18:29
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    $\begingroup$ @alexP The premise of the scenario started with the hero having "a mutation that allows him to easily pass on the Dragon gene". If that mutation is also passed on, then standard inheritance patterns don't need to hold. Perhaps something akin to gene drive? $\endgroup$
    – Tyler
    Aug 1, 2023 at 18:53
  • $\begingroup$ I cannot accept this answer since I already accepted one, but consider this one 'accepted' - both this and the answer about lactose tolerance is exactly what I need. Thank you so much, this is super helpful! $\endgroup$
    – shinobody
    Aug 2, 2023 at 21:07

A few hundred years

His children are probably all gonna be able to start harems with their super powers, or romance many. They'll likely become nobles or kings, do as nobles and kings do, and start dynasties centered around super powers. They'll have sex with servants and maids and such and spread the genes among the commoners.

As such, within two or three generations most nobility are likely to be controlled by super heroes, and from there the genes will quickly spiral out.

Here's a timeline.

60 years. A number of his children, and their children, meet up, decide they want to run things and start conquering the local countries. Superpowers give them an overwhelming advantage as warlords. They form clans with unstoppable power.

80 years. Most local powers are pacified, they breed a lot more.

120 years. The superheroes start to be overpopulated, have some civil wars, and a lot of them fly away to conquer new lands.

160 Vicious wars are fought, and the superhero groups overwhelm native superheroes and start to conquer new lands.

200 Two generations on, they get settled, over populate, and start to fight civil wars against their fellows, and wars against those around them.

This then repeats for a few cycles. It probably is a very bad time to be a mortal hero. Superheroes will use their powers to pretend to be gods or super beings and try to use you in wars to contest against their fellow supers. The faster breeding clans of supers quickly spread out.

  • $\begingroup$ Not really. Superpowers are a recessive trait, so most people who possess the gene do not get superpowers. And there's a matter of 'superpower lottery', where some people's powers might be mundane or useless - if you read My Hero Academia, consider how main character's mom has 'power of attracting small objects'. People at Superman level are extremely rare. $\endgroup$
    – shinobody
    Aug 2, 2023 at 21:04
  • $\begingroup$ So, an incestuous dynasty would spread it? You didn't say the mutated gene was still recessive, so I wasn't sure about that. You don't need superman powers to conquer a country. A lot of superheroes with low grade powers would be overwhelming against medieval people without guns or high tech stuff. $\endgroup$
    – Nepene Nep
    Aug 2, 2023 at 23:33
  • $\begingroup$ Not really. Most powers are minor or unimpressive, while some cause people with the genre to be disfigured or disabled. Some aren't viable and die before or right after birth. $\endgroup$
    – shinobody
    Oct 17, 2023 at 3:39
  • $\begingroup$ That's not really an issue for harems. Imagine how a modern day person with a machine gun could dominate medieval battlefields. You just need that level of power. If someone had two hundred children, would they on average get at least one machine gun level power? $\endgroup$
    – Nepene Nep
    Oct 21, 2023 at 14:16

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